Jk. Trimmer et al., Autoregulation of glucose production in men with a glycerol load during rest and exercise, AM J P-ENDO, 280(4), 2001, pp. E657-E668
Citations number
38
Categorie Soggetti
Endocrinology, Nutrition & Metabolism
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-ENDOCRINOLOGY AND METABOLISM
Related to hepatic autoregulation we evaluated hypotheses that 1) glucose p
roduction would be altered as a result of a glycerol load, 2) decreased glu
cose recycling rate (Rr) would result from increased glycerol uptake, and 3
) the absolute rate of gluconeogenesis (GNG) from glycerol would be positiv
ely correlated to glycerol rate of disappearance (R-d) during a glycerol lo
ad. For these purposes, glucose and glycerol kinetics were determined in ei
ght men during rest and during 90 min of leg cycle ergometry at 45 and 65%
of peak O-2 consumption ((V)over dotO(2) peak). Trials were conducted after
an overnight fast, with exercise commencing 12 h after the last meal. Subj
ects received a continuous infusion of [6,6-H-2(2)]glucose, [1-C-13] glucos
e, and [1,1,2,3,3-H-2(5)]glycerol without (CON) or with an additional 1,000
mg (rest: 20 mg/min; exercise: 40 mg/min) of [2-C-13]- or unlabeled glycer
ol added to the infusate (GLY). Infusion of glycerol dampened glucose Rr, c
alculated as the difference between [6,6-H-2(2)]- and [1-C-13] glucose rate
s of appearance (R-a), at rest [0.35 +/- 0.12 (CON) vs. 0.12 +/- 0.10 mg.kg
(-1).min(-1) (GLY), P < 0.05] and during exercise at both intensities [45%:
0.63 <plus/minus> 0.14 (CON) vs. 0.04 +/- 0.12 (GLY); 65%: 0.73 +/- 0.14 (
CON) vs. 0.04 +/- 0.17 mg.kg(-1).min(-1) (GLY), P < 0.05]. Glucose R-a and
oxidation were not affected by glycerol infusion at rest or during exercise
. Throughout rest and both exercise intensities, glycerol R-d was greater i
n GLY vs. CON conditions (rest: 0.30 <plus/minus> 0.04 vs. 0.58 +/- 0.04; 4
5%: 0.57 +/- 0.07 vs. 1.19 +/- 0.04; 65%: 0.73 +/- 0.06 vs. 1.27 +/- 0.05 m
g.kg(-1).min(-1), CON vs. GLY, respectively). Differences in glycerol R-d (
DeltaR(d)) between protocols equaled the unlabeled glycerol infusion rate a
nd correlated with plasma glycerol concentration (r = 0.97). We conclude th
at infusion of a glycerol load during rest and exercise at 45 and 65% of (V
)over dotO(2 peak) 1) does not affect glucose R-a or R-d, 2) blocks glucose
Rr, 3) increases whole body glycerol R-d in a dose- dependent manner, and
4) results in gluconeogenic rates from glycerol equivalent to CON glucose r
ecycling rates.